The Joy of Interlacing: Video Answers Everything You Were Afraid to Ask About Interlacing

As it happens, interlacing is not a diabolical technology invented just to make your life miserable by creating those annoying Venetian Blind patterns on digital videos. (Who knew?)

The wonderful people of Videopia don’t just explain interlacing – they defend it, starting with its early history. Then they explain how to deal with removing interlacing in the progressive-scan world of Internet distribution. And if you’re still not clear on when that horizontal pattern of lines on your video is a good thing and when it’s a bad thing, this will make it clear.

It’s by far the single best explanation I’ve seen, and they’ve done it all with fantastic production values.

Now if people will just watch the darned thing, maybe we won’t see all this poor deinterlacing in online videos on YouTube. (Stats were surprisingly low when this came online, so have at it, Visualist Nation, and spread the love around!)

Any further tips (or questions) to add to their interlacing advice, ye tech-savvy visualists? Let us know in comments.

Updated: Richard Lainhart writes with a still-better technique. I agree, absolutely – got so distracted by the elegant explanation of interlacing itself and its history that I neglected to pay as much attention to what they were actually suggesting! Of course, this won’t work in all cases, meaning you’re back to the video technique. But since a lot of you have cameras capable of shooting as Richard describes, this could be helpful.

The deinterlacing techniques mentioned in the video all will introduce artifacts of some sort in the image. If you use leave the fields in, you’ll still see interlace combing on the edges of objects in motion, even if the frame isn’t paused. Interpolated interlacing can be better, but you’ll still often see blockiness, sawtooth effects, or other such artifacting on straight lines and hard-edged objects, as no interpolation method is perfect.

If you can, you’ll get better results with this method – shoot everything in full 1080i HDV, and reduce the frame to one-half resolution in After Effects. When you bring the HDV footage into AE, convert it to square pixels but tell AE to not deinterlace it (in the Interpret Footage dialog.) Then scale that image to half-size in a 960×540 comp. This has the effect of throwing out every other field and reducing the frame to widescreen SD format, and you’ll get perfect, clear progressive full frames. From there, crop to 4:3 for standard SD, or scale up to 1280×720 for 720P HD – scaling the image up in AE will introduce some softness, but it will still look better than 720i footage when viewed on a computer screen.

All the footage on my YouTube site was processed this way, and none of it has any visible field artifacting.

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